Galin Iliev's blog

Software Architecture & Development on IIS7 performance data

You know, right? :) This the corporate web site of the biggest software company and the very wanted target of every hacker (or wanna-be hacker). When this website (or some other Microsoft websites like is down or show an unexpected error there are screenshots on the web (and blog posts) and this become a news of the day in software world :) - or at least on web dev world.

So now imagine of you are decision maker for hosting platform!? or hardware behind it?! or setting a bandwidth :)?! There is very little room for mistakes, huh?

And still is hosted on IIS7 .. since Beta3 (post is from June 15th, 2007). When Microsoft trust enough on IIS7 and host such important site on it, why you can't?

There is no doubt that the configuration behind is interesting so here is it:

=============== configuration ====================


  Model: HP DL585 G1 (4 dual-core CPUs)

  RAM: 32GB 


  Windows Server 2008 RTM (Build: 6.0.6001.18000) Enterprise version x6

  Number of clusters: 4 (in multiple datacenters)
  Machines in each cluster: 20
  Total machines: 80
Load Balancing:
  Hardware load balancing solution is used. The load balancing algorithm we are using is based on “Least Current Client Connections” to each load balanced member server of the cluster (not round robin, or other any other load balancing algorithms). The hardware load balancer will maintain the same number of current client connections to each member of the cluster. So if a W2K8 server is completing web requests faster than a W2K3 server, the load balancer will send more traffic to the server W2K8 RTM server.


Recently some performance data has been released on TechNet and here is what it says:

  • Win2008/IIS7 process more Requests per second(RPS) than Win2003/IIS6.
  • Due to #1 Win2008's CPU is more utilized.
  • As Win2008/IIS7 is performing better the load balancer send more requests to it.


Server Efficiency (RPS/ CPU %) – Efficiency of serving live web platform traffic

W2K3 SP2 4.36 “requests per CPU cycle”

W2K8 RTM 4.84 ~ 10.9% increased efficiency

CPU Utilization (%)

W2K3 SP2 44.8%

W2K8 RTM 52.8% ~ 17.9% degradation (This is impacted by the increased RPS the W2K8 servers are handling)

Web Service – Total Methods Requests/Sec (RPS)

W2K3 SP2 194

W2K8 RTM 255 ~ 31.4% more traffic is being sent to the W2K8 RTM servers

Web Service – Current Connections

W2K3 SP2 280

W2K8 RTM 294 ~ 5% increase

Load Balancing – Current Client Connections

W2K3 SP2 116

W2K8 RTM 116 Equal – as the hardware load balancer maintains the same amount of outstanding open client connections.

.NET CLR Memory – % Time in GC

W2K3 SP2 1.1%

W2K8 RTM 2.5% No significant degradation in “Time in GC


Source: Operations blog post on TechNet.

IIS7 is really next generation web platform...